Geochemistry/geochemical cycles

In the geochemistry of fluorine, the close match in the ionic radii of fluoride (0.136 nm), hydroxide (0.140 nm), and oxide ion (0.140 nm) allows a sequential replacement of oxygen by fluorine in a wide variety of minerals. This accounts for the wide dissemination of the element in nature. The ready formation of volatile silicon tetrafluoride, the pyrohydrolysis of fluorides to hydrogen fluoride, and the low solubility of calcium fluoride and of calcium fluorophosphates, have provided a geochemical cycle in which fluorine may be stripped from solution by limestone and by apatite to form the deposits of fluorspar and of phosphate rock (fluoroapatite [1306-01 -0]) approximately CaF2 3Ca2(P0 2 which ate the world s main resources of fluorine (1). 

Medical geochemistry (also referred to as environmental geochemistry and health Smith and Huyck (1999), Appleton et al. (1996)) can be considered as a diverse subdiscipline of medical geology that deals with human and animal health in the context of the Earth s geochemical cycle (Figure 1). Many medical geochemistry studies have focused on how chemical elements in rocks, soils, and sediments are transmitted via water or... 

Humic substances are clearly the major constituent of organic matter in lake sediments and therefore should play the central role in the geochemical cycle of carbon compounds in lakes, lake sediments, and sedimentary rocks. The characteristics and geochemistry of humic substances in lake sediments is described in this work by citing research done by the author and his coworkers, some of which is unpublished. 

Geochemical cycle. In geology and geochemistry, the reservoirs and fluxes depicted in Fig. 4-1 are often referred to as the geochemical cycle. It might as well have been called the geophysiochemical cycle. 

The slow carbon cycles are intimately connected with the geochemical cycles of sedimentary rocks, which involves all crustal elements. Although our interest is focused on carbon, we must discuss some related elements but can do so only superficially. For aspects not covered, especially those of mineralogy, reference is made to the geochemistry texts of Krauskopf (1979) and Garrels and MacKenzie (1971). 

Holser WT, Schidlowski M, Mackenzie FT, Maynard JB (1988) Geochemical cycles of carbon and sulfur. In Gregor CB, Garrels RM, Mackenzie FT and Maynard JB (eds) Chemical Cycles in the Evolution of the Earth. John Wiley Sons, New York, p 105-173 Hunt JM (1972) Distribution of carbon in crast of earth. Am Assoc Petrol Geol Bull 56 2273-2277 Hunt JM (1979) Petroleum Geochemistry and Geology. W. H. Freeman, San Francisco Jannasch HW, Wirsen CO (1979) Chemosynthetic primary production at East Pacific sea floor spreading centers. BioSci 29 592-598... 

N. Shikazono, Environmental and Resources Geochemistry of Earth System Mass Transfer Mechanism, Geochemical Cycle and the Influence of Human Activity, DOI 10.1007/978-4-431-54904-8 l, Springer Japan 2015... 

Shikazono N (2003) Geochemical and tectonic evolution of arc-back arc hydrothermal systems implication for the origin of kuroko and epithermal vein-type mineralization and the global geochemical cycle. Developments in geochemistry 8. Elsevier, Amsterdam Walther JV, Wood BJ (1986) Fluid-rock interactions during metamorphism, vol 5, Advances in... 

In summary, extensive research has been carried out on the lanthanide geochemistry of marine hydrothermal vent systems. Lanthanides are good indicators of water/rock reactions between hydrothermal fluids and basalt, and reactions between Fe oxide particles and seawater. While the lanthanides undergo an active geochemical cycle in and above venting fluids, this cycle is not quantitatively significant with respect to river water fluxes and oceanic cycles and inventory. 

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